The field of art to which this invention pertains is organophilic modified clays.
Organophilic clays which are compatible with organic liquids have been known for some time. Their preparation and various uses have been described in, for example, U.S. Pat. Nos. 2,531,427 and 2,966,506. As taught by these references, naturally occurring water dispersible clays, such as montmorillonite, are reacted with "onium" compounds to produce organic clay complexes which are compatible with organic liquids.
In order to obtain maximum dispersibility and maximum thickening or gelling efficiency using organophilic clays, it has been necessary to add a low molecular weight polar organic compound to the composition. Such polar organic compounds have been called polar activators, dispersants, dispersion aids, solvating agents, and the like. Methanol is an example of a useful polar compound.
Organophilic clays which are said to have enhanced dispersibility in organic systems without using a polar activator are described in U.S. Pat. No. 4,105,578. Such organophilic clays are made from the reaction of a smectite-type clay with a methyl benzyl dialkyl ammonium compound wherein the alkyl groups contain at least 16 carbon atoms.
Organophilic clays having enhanced dispersibility in organic systems are also described in U.S. Pat. No. 4,412,018. These compositions are made by reacting a smectite-type clay with an organic anion, such as an organic acid, and an organic cation, such as a quaternary ammonium compound.
Other organophilic clay are described in U.S. Pat. Nos. 4,434,075, 4,434,076 and 4,450,095.
A particular use for organophilic clays, such as those claimed in U.S. Pat. No. 4,105,578, is described in U.S. Pat. No. 4,081,496. As taught by this invention, the organophilic clay is mixed with an unsaturated aromatic monomer, e.g., styrene, to form a pregel which is then combined with an unsaturated polyester to form a thixotropic composition.